1. NDnano Undergraduate Research Fellowship (NURF)
2015 Project Summary
1. Student name: Edward Hunckler
2. Faculty mentor name: Susan Fullerton
3. Project title: Removing surface residue from graphene via CO2 annealing
4. Briefly describe any new skills you acquired during your summer research:
During this summer, I learned several new techniques. The first is Atomic Force Microscopy
(AFM). I learned how to produce high-resolution scans with this machine. I also used the Glove
Box because the AFM was housed inside. Finally, I learned how to work inside of a cleanroom
where I operated the Nanotube Furnace to anneal my samples in a CO2 environment.
5. Briefly share a practical application/end use of your research:
This research will be used to clean the surface of graphene for use in nanoionic memory –
a new type of flash memory that utilizes two-dimensional crystals and lithium ions. The first
generation of the memory consist of a graphene transistor with an ordered monolayer of
cobalt crown ether phthalocyanine (CoCrPc) molecules deposited on the graphene surface.
In order to achieve an ordered monolayer of CoCrPc, the underlying graphene must be
atomically clean. During the fabrication of these devices, a significant amount of residue
remains on the graphene surface - primarily polymethyl methacrylate (PMMA), a polymer
commonly used in electron-beam (e-beam) resist and as a transfer layer for graphene
prepared by chemical vapor deposition (CVD). Gong et al.1 demonstrated that a CO2 anneal
can remove PMMA residue from graphene.
This summer, I scaled-up this process to larger sample sizes (1 x 1 cm) and
quantified the amount of residue using atomic force microscopy. To determine the optimal
annealing temperature and time, CVD graphene with PMMA residue was imaged before and
after the CO2 anneal. A CO2 anneal at 500˚C for 30 minutes was optimal for cleaning the
graphene. Exfoliated graphene flakes exposed to PMMA were tested to verify the
effectiveness of the anneal. The CO2 anneal reduced the surface roughness by an order of
magnitude. In addition, the procedure was used to remove e-beam resist from graphene
flakes, and the results showed a similar reduction of the residue.
This work was sponsored by the NSF through an REU supplement to grant # ECCS-GOALI-
1408425 .
[1] Gong, C, et al. Journal Of Physical Chemistry C, 117(44), 23000-23008.

2. Fig. 1: Edward Hunckler working with the AFM in the glove box
Fig. 2: Graphene clean by CO2 annealing
Publications (papers/posters/presentations):
E. Hunckler, E. Kinder, S. Fullerton “Removing surface residue from graphene via
CO2 annealing” NURF Research Presentation (Oral) 7/22/2015
E. Hunckler, E. Kinder, S. Fullerton “Removing surface residue from graphene via
CO2 annealing” Notre Dame Undergraduate Research Symposium (Poster) 7/31/2015